Process for casting molten metal in molds.



C. CRAWFORD. PROCESS FOB. CASTING MOLTEN METAL IN MOLDS. APPLICATION mumJUNE-14, 1900.

1,040,,5 1 7, Patented Oct. 8, 1912.

VI/IIII/Il/M SATES T TWICE.- k

CLAY cnnwroan, or TOLEDO, OHIO, ASSIGNOR To 0. s. BRIGHAM, or TOLEDO,c1110.

-IROCESS FOR CASTING MOLTEN METAL IN MOLDS.

Patented Oct. 8, 1912.

To all whom it may concern:

Be it known that I, CLAY CRAWFORD, a

I citizen of the United States, residing at 815 West Woodrufl avenue, inthe city of Toledo, county'of Lucas, and State of Ohio,

have invented new and useful Improvements in Processes for CastingMolten Metal in Molds, of which the following is a specification.

This invention relates to the process of casting molten metal in moldsand has for its object: First. The separation and elimi nation of thecontained slags, segregates and gases,'which cause flaws and otherdefects. Second. Also to break up the axes and planes of cleavage in theforming crystals, which weaken the resulting casting. Third. To form andretain to the end of'the solidifying period a feeding head to reduce orprevent piping, or a honeycombed core along the central axis of thecasting.

I shall describe ,my'invention with refer-' ence to the accompanyingdrawing of a machine for casting steel ingots by this process.

The machine used herein for illustration is the subject of anapplication for a patent now pending, filed October 21st, 1907, Number398,498, but which can be used for many other forms of castings.

It consists of a mold mounted on a table, supported on the top end of avertical shaft, with means to rotate the mold about its ver tical axis,with a constantly varying speed of rotation, cooperating simultaneously,with means to accelerate the cooling of the lower portion of the moldand casting, and to retard the cooling of the upper portion.

Among engineers it is a well known fact that metal castings, especiallyof steel, are not perfectly homogeneous and their reliability and valueis much reduced by these defects. During all the time the liquid metalis cooling there are processes going on by which the carbon, phosphorus,slags and sulfur are being segregated, and the segregates concentratedin the central portion of the mass, and being lighter than the moltenmetal, most of them rise to the upper portion or surface of the core ofmolten metal.

In the manufacture of steel as now conducted, a portion of the upper endof the ingots are cut oil and scrapped, causing a great loss ofmaterial, but even then the central portion of what is left is notuniform with the outside portion, and contains slags,

segregates, blowholes, and holes caused by the solidification of anoutside shell and the shrinkage of the inner portion as it cools,leaving a honeycombed core. Bolling or hammering while the ing'ot ishighly heated partially remedies some of these defects but not whollyso.

The process by which I reduce or elimihate-the defects in the castshapes to which it is applicable, is to oscillate or rotate with aconstantly varying speed of rotation, the mold about its vertical axis,and at the same time regulate the cooling of the molten metal, so thatthe solidification shall proceed progressively from the bottom and sidesof the mold and ending at the center of the upper surface. This leavesan avenue open for the escape of impurities, as they concentrate in thecenter and rise to the surface, if not prevented by the upper ortionsolidifying. This also gives a ceding head to supply metal to correctthe shrink= age due to solidification. The rotation of the mold aboutits vertical axis, with a constantly varying speed of rotation, causesevery particleof the liquid metal to slide over the surface of everyadjacent particle, which agitation separates the impurities and theyrise to the upper surface of the core of liquid metal, and they canafterward be separated by cutting them off the upper end of the ingot.about its vertical axis to get the same effect as rotation with aconstantly varying rota tive velocity. A box shaped mold may be mountedon rollers and oscillated or shaken in a horizontal plane with thecooling of the top portion retarded, and the coolingo'f .the bottomportion accelerated, to get the same effect as by rotation with aconstantly varying rotative velocity. In other words, the process in itsbroadest aspect may be said to consist in agitating a body of moltenmetal during the cooling of the same.- Such agitation causing theunfrozenor molten metal to move or slide over the surface of thatportion of the metalwhich has already solidified. More specifically, theprocess in eludes the production of the agitating movement by moving themetal to be cast with varying or unequal velocities in equal intervalsof time.

It is a law of the molecular aggregation of crystalline solids that whentheir particles consolidate" under the influence of heat and The moldmay he oscillated motion, their crystals arrange andgroup themselveswith their principal axes in lines perpendicular tothe cooling surfacesof the solids. In castings of rectangular section 5 these axes meet atpoints equidistant from the cooling surfaces, and are there imperfectlyconnected and form a core or seam, which will contain a varying amountof slag or other impurities, which form a cleavage lane that is easy torupture, and which it is impossible to remoye by subsequent working withrolls or hammers. This form of crystallization is nicely shown in a cakeof artificial ice. In molds of circular cross section there is aptto be.a flow of impurities to the center of theingot, forming a vertical cpreor pipe. My process of constantly slidmg the liquid metal over thesurfacesof the solidified metal breaks up the axes of crystallization,and at the same time separates the impurities, which rise to the surfaceand gives much stronger castings,1 free from coarse planes of cleavage,and better adapt ed to after-treatment with rolls and her. :mferenceshould be had to the accom- .panylng drawings forming'a part .of thisspecification in which Figure 1 is a front elevation of the mechanlsmfor rotating the mold; 2 is an end elevation of the mechanism forrotating the mold and Fig. 3 is a front'elevation, partly in section, ofthe mold and apparatus forrotating the same. 1 Referring to'theaccompanying drawing, 1 is the frame of the machine, 2 is a hollow,vertical shaft, supported by frame 1, and having secured on its upperend a table 3, which hasv a flange extending from its outercircumference; resting-on table 3 is' a plate 15, which formsa bottomfor the ingot mold 16., A portion oft-he upper end of the ingot mold maybe enlarged and lined with a belt' 17 cf a non-conductor of heat toprevent rad ation of heat and retard the cooling of theliquid metal 19,and 18 is a covering of a non-conductor of'heat on the upper surface ofthe molten metalto prevent the radiation the cooling process. .1

20 is metal that has solidified. around the sides and-bottom of themold. I 21 are: pipes thatmay be used to throw t5 jets from holes 22offa' cooling fluid. "(as' a mistiof air and water) on the lowers-and:-

ou'ter surface'of the mold, tejiacpeleratefthe cool of the metalzfmtha't'ipbrtion of; the

. These j ts are controlled the an, m be pp l-p cesivel from he I of:heat from the upper-surface of the liquid the Bxtmme metal, and retardthe solidification of the surface of them etal to the very last end of Ytousoli.

process is to keep the to o surface of the mo ten metal. This 'rotat pmerging "1% into the outer surface .dilftti l'iilg mo d as theyrise.furnish radiating surface for .the pose-of accelerating the cooling ofthe contained metal at its lower end.

Instead of lining 17 ,"a belt of a non-.con-

ductor of heat may be used .to cover the outer surface of theupper endof the mold to obtain the same results as those obtained by lining 17. 1

On the vertical shaft 2 is a beveled gear 4 meshing into gear 5 on shaft7, supported by bearings 6; on shaft 7 is crank 8, having a pin 9, onwhich is box 10, sliding in a slot in crank 11, on the endof shaft 13,which is turned by a belt on pulley 14. The shafts 7 and 13 areparallel, but not in the same line,

13 being shown a little higher than 7 and as they rotate with a meanangular velocity the angular velocity ratio at each instant 1s varyingin the position shown the angular velocity of gear 4 would be at aminimum,

and with the cranks pointing downward it would be at its maximumvelocity.

The mode of operation is to.-rotate the table and mold with a constantlyvarying speed of rotation, then fill the mold with molten metal from aladle in the usual manner, then cover the upper surface of the moltenmetal with a non-conductor of heat,

as 'air-slaked lime, to prevent the radiation of heat as much aspossible, then, if necessary, apply the cooling fluid from the lowestring of jets and progressively at intervals to the upper ring of jets asmay be needed to cool the metal progressively from the bottom upward.The efiect of this process of re-' tarding the cooling of the upper endof the casting and the accelerating the cooling of its lower end soonforms the shell 20 of solidified steel next the bottomsides of the mold,with the sides of the shell 20 decreasing gradually in thickness towardthe top ,port1on,' aiid during the process .of cooling there will be acore 19 inverted conoidal shape, which will con-' stantly decrease insize as the cooling proceeds until it finally disappears at the centerof'thetop-of the casting. The center of top surface being the last pointOne of'the most important oints of my the molten of molten metal of Imetal liquidto the end 0 the solidifying stage, and thus 'to furnish afeeder to up the space left in the interior of the casting due to theshrinka e ofthecontained cooling metal, this liqui core also furnishesan outlet for the contained slags, segregates and gases to esca e outthrough the upper of the mold with a constantly va spec of rotationkeeps every parti' e of the ac htrffilhe ho and anger e" it. Also theagitation brings t e particles one another is-caused by the resistanceof their inertia to a change in their rotative velocity about the axisof rotation, and by their friction on the surface of the solidifiedmetal and on each other. This sliding and agitation, separates the slugsand nodular segregates and also the occluded gases, and as they'arelighter than the molten metal, they arise to its surface and se aratefrom of oxid of iron in the molten metal into con tact with the carbonand it is'reduced to metallic iron.

. hammering or rolling. I

When castings are allowed to solidify on their upper surface while theinterior is molten, shrinkage causes a honeycombed core in the interior,which in effect are 'flaws and cannot be eliminated by subsequenteliminate this 'center by, eeping the upmold around its vertical axis. A

Changes may be made in some of the minor details while the essentialfeatures are retained, and thespirit of th invention embodied.

Having described my invention and its gene'ralmethod of operation what Iclaim is 2-- 1. The process of casting, which consists in introducingthe metal into a mold, causing the metalto cool more rapidly in one"part of the mold than in the others and im ltaneously causing theparticles of the eatly reduce or unsolidified metal to move with respectto each other and to the solidified metal during the cooling.

2. The process of casting, which consists in introducing the metal'intoa mold, coolin the'mold rogressively from one end toward the oppositeend thereof and simultaneously causing the particles of the unsolidifiedmetal to move with respect to each other and to the solidified metalduring the cooling.

3. The process of casting which consists in rotatin a body of moltenmetal within-a mold, t roughout a succession'of time 'periods, thevelocity of rotation of the mold varyin during each time period.

4. T e process of casting, which consists in introducing the metal intoa mold, subje'cting the mold to rotary motion so that the same moveswith unequal velocities in equal intervals of time and simultaneouslycooling one portion of the mold more rapidly thanthe other portions.

5. The process of casting, which c nsists in moving the body of metalwith un ual velocities in equal intervals of time and simultaneouslypreventing the radiation of heat from a certain ortion of the metal andcooling another portion of the metal.

6. The process of casting, which consists in introducing the metal intoa mold, rotating the mold with unequal velocities in equal intervals oftime and preventing the radiation (13f heat from the exposed surface ofthe meta CLAY CRAWFORD.

Witnesses GHABpEs SPRAGUE, Gannon. KING.

